The present invention relates to a heat recovery system, in particular, a vehicle heat recovery system which generates motive energy by recovering exhaust heat from a combustion engine, which is a drive source of the vehicle.
A known vehicle exhaust heat recovery system generates motive power by driving a turbine using coolant water (high temperature vapor) that has been heated by the heat generated by an internal combustion engine. The motive force drives a generator that is operatively connected to the turbine for generating electric power (see for example Japanese Laid-Open Patent Publication 2000-345915).
However, the known structure for driving the turbine by means of the coolant water of the internal combustion engine has low energy conversion efficiency from thermal energy (exhaust heat from the engine) to mechanical energy (motive power generated by the turbine) since the expansion ratio of the coolant water is high. In order to improve the conversion efficiency, it is necessary, for example, to broaden piping or conduits comprising the coolant water circulation circuit or to increase the size of the turbine in its radial direction. This causes a problem of a vehicle exhaust heat recovery system that is large in size and which is difficult to be installed into the vehicle.